evaluation of gravelless pipe systems for onsite wastewater
EVALUATION OF GRAVELLESS PIPE SYSTEMS FOR ONSITE WASTEWATER TREATMENT ACROSS MINNESOTA INTRODUCTION S. H. Christopherson, D. M. Gustafson, J. L. Anderson Approximately 30% of Minnesota's residents rely on onsite technologies for their wastewater treatment. Gravelless pipe systems became a standard choice for trench systems in 1989 in Minnesota Rules Chapter 7080. This system is called gravelless because no rock or gravel is placed in the trenches. The gravelless pipe evaluated in this study was 10” inner diameter corrugated polyethylene tubing covered with a permeable nylon fabric. Two rows of holes, approximately 1/2 inch in diameter are located at the four o’clock and eight o’clock position. Sizing requirements for these systems are based on research performed at the University of Minnesota in the early 1980s (Anderson, 1985). Figure 1. Installation of gravelless pipe The Minnesota Onsite Sewage Treatment Contractors Association (MOSTCA) received concerns from its members about gravelless pipe systems in 1999. MOSTCA contacted several suppliers of gravelless pipe who agreed to fund a research study to see if problems do, in fact, exist. The purpose of this study was to determine the reason(s) for success and failure of Individual Sewage Treatment Systems that use gravelless technology in Minnesota.